[dev] code upgrade checking

[Marko]

hi

anyone thought about putting a common horde feature whereby if a developer makes
a drastic code change, for example concerning the way the data is stored
internally to horde, a script could be attached to fix any old data.

so some maintenance function would run a code check, either manually entering a
script path or during horde init, then if a fix script is found it is run,
upgrading also the data to the new code level.

the fix scripts could be left behind in a trail, so even if someone is going
from code version .3 to code version .9 it would go through any scripts
incrementally.

marko